In lines 4 to 12 you see how to configure p:ajaxStatus. It is triggered every time when a AJAX request is fired, e.g. when a p:commandButton is pressed. As soon as the request is fired, the content of the start facet is shown. As soon as the request ends, the content of the complete facet is displayed.

If you wish not to trigger p:ajaxStatus on a p:commandButton, then you have to set the global attribute to false like in line 15.

p:blockUI does work differently, Here you have to define which components are blocked (block="panel") and which component triggers the block (trigger="btn"). See lines 20 to 23.